Exit polls conducted by ABC News on “Super Tuesday” show that more than 60 percent of GOP voters in five states favor Trump’s proposed ban. In Alabama and Arkansas, that figure rises to nearly 80 percent. Trump won seven of the day’s 11 state primaries.

That kind of support is generating alarm.

“When you open the door to defining what religion isn’t sufficiently American, does anyone think it’ll stop with Muslims?” says Haroon Moghul, a fellow at the Institute for Social Policy and Understanding. “Trump himself is dangerous as a candidate, but his proposals now open the door to people who are even more dangerous.”

Trump first announced his proposal to temporarily ban Muslims from entering the United States last December. In a statement issued at the time by his campaign, Trump promised a “total and complete shutdown of Muslims entering the United States,” until the government “can figure out what is going on.” He later reiterated this proposal in the face of public outcry, emphasizing in a speech that his policy of banning Muslims would continue, “until we find out what the hell is going on.”

And his position now enjoys widespread support, even among Republican who voted for other candidates. Many of those who supported Trump’s proposal actually voted for his main rival, Ted Cruz.

Even “establishment” candidates like Marco Rubio have gone on record describing discrimination against Muslim-Americans as a “fiction.”

And its not confined to the Republicans. A Fox News poll this December showed that even among Democrats there was broad support for the measure — as long as it was not identified with Trump himself. Some 45 percent of those polled favored banning Muslims when the plan was not identified as a originating with Trump. When Trump’s name was mentioned however, support dropped to 25 percent.

“When people in positions of power articulate extreme opinions, they make it even easier for ideas on the margins to become respectable,” says Moghul. “In the eyes of some, policies like these could even start to look desirable.”